Soft Magnetic Composite Vs. Laminated Steel: Uses & Limitations.

Posted by Horizon Technology - July 09, 2018

The demand for all things newer and better in technology has spread to electric motor applications. The traditional lamination (electrical) steel motor construction is being challenged by the emergence of powder metal parts made from soft magnetic composite.

Think of laminated steel parts as the safe, old-school way to build electric-based parts. Meanwhile, soft magnetic composites (SMCs) are unfamiliar but represent huge untapped potential for motor and other, similar applications.

Here are the qualities that make soft magnetic composite and laminated steel different from one another. By the time you’re done reading this, you should have a good idea which direction to take your next project.

Magnetism: Soft Magnetic Composite Vs. Laminated Steel

What’s arguably the biggest factor in how the magnetic properties of a component turn depend strongly on their manufacturing process.

For laminations, that process can include:

  • Punching
  • Stacking
  • Welding
  • Riveting
  • Pressing

This series of processes deforms the interior of the material, resulting in weaker magnetic properties.

Because ferromagnetic materials (like SMCs) have a different structure, you’ll see a different distribution of magnetic losses in them.

For starters, the hysteresis losses (energy wasted in the form of heat) in SMCs are higher. BUT, eddy current losses are much lower in soft magnetic composites. SMCs have higher hysteresis loss because they’re harder to magnetize. Their eddy losses are lower because the tiny composite particles are so isolated.

Combining these two stats gives you the total loss characteristics of any magnetic material. But what you really need to know is that the superior magnetic stats of SMCs can lead to new ideas impossible with traditional laminations. Keep reading:

2D Vs. 3D

Old-school steel laminate motor construction is limited to 2D magnetic flux so you don’t lose too much magnetism in the direction perpendicular to the laminate. A perfect example of this is the radial flux motor.

Because soft magnetic powder composites create a 3D magnetic flux path, your possibilities expand exponentially. 3D opens the door for unique and higher-performance designs and ideas in motors.

SMC material’s makeup combined with its net shaping capability allow you to introduce new 3D solutions with minimal iron (magnetic) loss and optimized copper winding. Even a standard motor’s performance and capabilities can be upgraded through unique design elements -- but only with SMC.

Power Density

Soft magnetic composites can increase the power density of electric machines. With smart, intuitive use, they can even surpass the power density of a machine made from lamination steels.

It’s true that laminations are fully dense steel, so you will see differences in raw material density compared with SMCs. But remember that with laminates, metal is being stacked and pressed into frames.

It’s like having to use a cookie cutter vs. being free to arrange the batter however you want.

How so? The unique design capabilities of SMC can offset some of those density differences. Laminations are punched from sheets of steel, but with SMCs you can add a dab of powder wherever you wish and move it around. This would let you, for example, add an outer lip to a small motor component so it can capture stray magnetic flux.

More on Applications Where SMC May Be Useful

As mentioned, powder metallurgy is the only process that can create net shape components -- gear box parts, motor parts, etc. -- for the auto industry.

Electric motor applications that may benefit from soft magnetic powder use include:

  • Axial flux motors
  • Transverse flux motors
  • Pancake (very flat) motor designs
  • Other motor types with unique designs

High-efficiency motors do their job best with electrical machines featuring 3D magnetic flux. In addition, there are emerging, new applications that need high operating frequencies. Soft magnetic powder composites are the answer because they offer ideal magnetic properties at superior frequencies.

This makes powder metal components perfect for applications with limited space. These applications include automobiles but also:

  • Robotics
  • Home appliances
  • Air conditioning
  • Compressors


Questions?

Density is always a question with powdered metal, but many of its design benefits make it still the clear choice over steel lamination -- in the right application. When you combine the 3D flux capabilities of SMCs with their ability to make the same product with fewer parts, there’s little reason to stick with tradition in the motor types and industries listed above.

Not every product is perfect for powdered metal. If you have questions about whether your project’s needs match up with SMCs’ capabilities, get in touch with us.

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Topics: Magnetics, Materials


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